THE EFFECTS OF REDUCED INFLATION PRESSURE ON SOIL-TIRE INTERFACE STRESSES AND SOIL STRENGTH

Inflation pressures as low as 41 kPa have been recommended by agricultural tire manufacturers for minimizing an oscillatory vibration problem, commonly called ''power hop''. Other benefits of these lower inflation pressures might include decreased soil-tire interface pressures, increased tire performance, and decreased soil compaction. Measurements of soil-tire interface stresses were made at four positions on the lugs and at three positions between lugs on an 18.4-R38 R-1 radial tractor tire operated at four combinations of dynamic load and inflation pressure. These measurements showed that as inflation pressure increased, the soil-tire interface stresses near the center of the tire increased, while the stresses near the edge of the tire did not change. The increased stresses near the center of the tire were also transferred to the soil as a compaction increase sensed with the cone penetrometer. ''Correctly'' inflated tires (i.e. lower inflation pressures) also improved net traction and tractive efficiency.